Method and apparatus for connecting underwater conduits

ABSTRACT

A method and apparatus for connecting underwater conduits and more specifically, to a method and apparatus which is capable of performing the diverless connection of underwater flowlines and connection of these flowlines to underwater structures such as flowline bases, xmas trees and templates. The connection of underwater conduits facilitated by the use of a remotely operated vehicle and connection apparatus both being launchable and recoverable by a support vessel. The connection apparatus adapted to mount on at least one of the underwater conduits and the connection apparatus allowing for docking of the remotely controlled vehicle which then captures and draws a second conduit to form a continuous flowline.

This application is a continuation of application Ser. No. 09/054,943filed Apr. 3, 1998.

1. INTRODUCTION

This invention relates to a method and apparatus for connectingunderwater conduits and, more specifically, to a method and apparatuswhich is capable of performing the diverless connection of underwaterflowlines—both flexible and rigid—in any combination of each other, andconnection of the said flowlines to underwater structures such asflowline bases, xmas trees, templates or similar.

There are various recognised methods of diverless connection ofunderwater flowlines to underwater structures. The methods used for suchconnections are characterised mainly by two principal factors; the useof permanently installed underwater hardware known as a tie-in porch orreaction structures and the strict dependency upon the relatedconnection system (connector). Both the permanently installed underwaterhardware and connection system are critical parameters. The items ofhardware required to support the connection operations are usuallyinstalled during flowline or underwater structure installation, anydeviation from standard procedures required by the installers couldresult in a very high cost impact making the system less competitivethan other alternative options Furthermore, the strict dependence upon agiven connection system can limit the use of the system to certainapplications.

The above reasons highlight the need for an alternative method which isable to overcome both the needs of permanently installed underwaterhardware and the dependence upon a given connection system whilstensuring the same operating reliability as existing systems. Inaddition, the selection of an intervention philosophy requiring the useof neutrally buoyant tools optimises the flexibility of the presentedmethod thus avoiding any dependency on the surface support vessel.

The aim of the present invention is to negate these drawbacks byproviding a system which allows fully remote connection of underwaterflowlines without using any permanently installed underwater hardware,allowing the use of any type of connection system, and performing allthe operations using only the remotely operated vehicle to install andoperate all the system's tools.

According to one aspect of the present invention there is provided amethod of connecting underwater conduits from a support vessel on thesurface comprising the steps of launching a remotely operated vehiclefrom the support vessel, launching connection apparatus from the supportvessel; manipulating the remotely operated vehicle to dock with theconnecting apparatus; installing the connection apparatus to one of theconduits; activating a docking clamp means using the remotely operatedvehicle to capture the end of the first conduit; activating theconnection apparatus to draw the second conduit to the first; connectingthe two conduits together to form a continuous flowline; providing asealed connection, and recovering the remotely operated vehicle andconnection apparatus to the support vessel.

Each of the above method steps are carried out without the need forunderwater personnel. Each step is monitored and controlled from thesupport vessel thereby increasing the efficiency and safety of theconnection process.

Additionally, the method includes the step of supporting the conduit ona frame above the sea bed.

Advantageously, the remotely operated vehicle carries out a survey ofthe work site and sends a report to the support vessel prior toconnection of the conduits

According to the further aspect of the present invention there isprovided an apparatus for connecting underwater conduits beingcontrolled from a support vessel on the surface, the apparatuscomprising a remotely controlled vehicle launchable and recoverable fromthe support vessel; connection apparatus launchable and recoverable fromthe support vessel; means for docking the remotely operated vehicle tothe connection apparatus; means for mounting the connection apparatus onone or both of the conduits; means provided for capturing the end of theother conduit and drawing the second conduit to the first to enable aconnection of the conduits to form a continuous flow line; means toeffect the connection and means for providing a sealed joint.

Advantageously, each of the connection apparatus is launched in a sledgefrom the support vessel.

Preferably, a support frame is also launched from the support vessel,the support frame being placed around one or both (depending on thefield layout) of the conduits by the remotely operated vehicle to raisethe conduit from the sea bed.

Advantageously, the frame is a light-weight metallic frame substantiallyH-shape in configuration.

Preferably an interface skid is provided which is connected to theremotely controlled vehicle, launchable and recoverable from the supportvessel, which allows the remotely controlled vehicle to dockmechanically, hydraulically and electrically to the connecting apparatusin order to provide power for the connecting apparatus.

Conveniently, an interface collar is provided on the free end of theflexible conduits to allow the connection apparatus to be mounted inposition on the flexible conduits.

Advantageously, buoyancy modules are provided in addition to the supportframe. These modules act along with the support frame thereby raisingthe conduit from the seabed to enable connection of the adjacent conduitto be carried out.

Conveniently, the support frame and the connection apparatus aresubstantially buoyant in water to enable manoeuvrability by means of theremotely operated vehicle.

Advantageously, the manipulation means on the remotely operated vehicleis an articulated arm having a closeable grab arrangement at the freeend thereof.

2. EQUIPMENT DESCRIPTION

Embodiments of the present invention will now be described withreference to and as shown in the accompanying drawings in which:

FIG. 1 is a side view of the “diverless flow line connection system”part of the connection apparatus, fixed to the underside of the remotelyoperated vehicle; one aspect of the present invention.

FIG. 2 is a side elevational view of a “deployment frame” for launchingand recovering the connection means from a support vessel on thesurface.

FIG. 3 is a side elevational view partly in phantom and partly in crosssection of an “interface collar” connected to a flexible pipeline.

FIG. 4 is a plan view of an “axial force tool” part of the connectionapparatus.

FIG. 4A is an end elevational view of the “axial force tool” of FIG. 4.

FIG. 4B is a side elevational view partly in phantom of the “axial forcetool” of FIG. 4.

FIG. 5 is a plan view partly in phantom and partly broken away of the“reaction tool” part of the connection apparatus.

FIG. 5A is a side elevational view partly in phantom and partly brokenaway of the “reaction tool” of FIG. 5.

FIG. 5B is an end elevational view of the “reaction tool” of FIG. 5.

FIG. 5C is an opposite end elevational view of the “reaction tool” ofFIG. 5.

FIG. 5D is a plan view partly broken away of the “reaction yoke” part ofthe connection apparatus.

FIG. 5E is a side elevational view partly broken away of the “reactionyoke” of FIG. 5D.

FIGS. 5F and 5G are each opposite end elevational views of the “reactionyoke” of FIG. 5D.

FIG. 6 is a plan view partly in phantom of the “flange connection tools”used to perform the connection between two conduits of bolted flangetype.

FIG. 6A is a side elevational view partly broken away of the “nutmagazine tool” one of the “flange connection tools” of FIG. 6.

FIG. 6B is a cross sectional view partly broken away of FIG. 6A showingthe “nut magazine tool”, one of the “flange connection tools”.

FIG. 6C is a plan view of the “bolt insertion and tensioning tool” partof the “flange connection tools”.

FIG. 6D is a side elevational view partly broken away of the “boltinsertion and tensioning tool” one of the “flange connection tools” usedto perform the connection between two conduits of bolted flange type.

FIG. 7 is a plan view of an “interface skid” to provide the interfacebetween the remotely operated vehicle and the connection apparatus.

FIG. 7A is an end view of FIG. 7.

FIG. 7B is a side elevational view of FIG. 7.

FIG. 8 is a side elevational view of an “H” frame for supporting a rigidconduit above the seabed.

FIG. 8A is a side elevational view of FIG. 8.

FIG. 9 is a side elevational view partly in cross section illustratingone of the ancillary tools used to support the connection apparatus.

FIG. 9A is a side elevational view of the “seal insertion tool” that isdeployed by the ROV manipulator in a carrier fitted with an ROV T-barhandle.

FIG. 9B is a side elevational view of the “seal insertion tool” alone asshown in FIG. 9A but without the bolt heads.

FIG. 10 is a side elevational view in phantom and partly broken away ofa “spoolpiece installation guide tool”.

FIG. 10A is an end view of FIG. 10.

FIG. 10D is a side elevational view of the “blind flange removal tool”.

FIG. 10C is an end elevation of FIG. 10D.

FIG. 11 is a side elevational view of the subsea utility wench.

FIG. 11A is a plan view of FIG. 11.

FIG. 11B is a side elevational view of FIG. 11A.

FIG. 11C is a side elevational view partly in phantom of a portion ofFIG. 11A.

FIG. 12 is a schematic view of the initial stage of the operation ofconnecting two conduits together, one of which is flexible.

FIG. 12A is a schematic view of the first stage of the operation inconnecting two conduits together, one of which is flexible.

FIG. 12B is a schematic view of a second stage of the operation.

FIG. 12C is a schematic view of a further stage of the operation.

FIG. 13 is a schematic view of a further stage of the operation.

FIG. 13A, B, and C are schematic view of a still further steps in theoperation.

FIGS. 14, 14A, 14B and 14C are schematic views of further steps in theoperation.

FIGS. 15 and 15A are schematic views of further steps in the operationin connecting a flexible conduit to a subsea structure.

FIGS. 16 and 16A are schematic illustrations of further stages in theoperation in connecting a flexible conduit to a subsea structure.

FIGS. 17, 17A, 17B and 17C are schematic views of successive steps inconnecting a rigid conduit to another rigid conduit.

FIGS. 18, 18A, 18B and 18C are schematic views of later stages inconnecting a rigid conduit to another rigid conduit.

FIGS. 19, 19A, 19B and 19C are schematic views of further successivesteps in connecting a rigid conduit to another rigid conduit.

FIGS. 20, 20A, 20B and 20C are schematic views of successive steps inconnecting a rigid conduit to another rigid conduit.

FIGS. 21, 21A, 21B and 21C are schematic views of successive steps inconnecting a rigid conduit to another rigid conduit.

FIGS. 22, 22A, 22B and 22C are schematic views showing a more detailedoperation sequence of the connection apparatus.

FIGS. 23, 23A, 23B and 23C are schematic views showing a furtherdetailed operational sequence of the connection apparatus.

FIGS. 24, 24A, 24B and 24C are schematic views showing a more detailedoperational sequence of the connection apparatus.

FIGS. 25, 25A and 25B are schematic views showing further detailedoperational sequences of the connection apparatus.

The apparatus for connecting the conduits together comprises a completeset of tools and equipment able to perform, but not limited to,connections of rigid conduits to flexible conduits and rigid conduits torigid spool pieces.

The said tools include a diverless flexible conduit connection system 10(FIG. 1) (hereinafter referred to as a DFCS), an axial force tool (AFT)20 (FIG. 4), a reaction tool (RT) 30 (FIG. 5), a reaction yoke tool(RYT) 31 (FIG. 5a). flange connection tools (FCT) 41 (FIG. 6) and 46(FIG. 6a), an interface skid (SKID) 50 (FIG. 7), and equipment used tosupport offshore operations including a lightweight H-frame (LHF) 60(FIG. 8) each of which will be described in greater detail below.

2.1 DIVERLESS FLEXIBLE CONNECTION SYSTEM

The said DFCS 10 which is shown in detail in FIG. 1 (for moreinformation refer to: Australian patent No 658239, U.S. Pat. No.5,593,249, Norwegian Patent No; 96, 1761 and United Kingdom Patent No;GB2300439) consists of a structural skid frame with winches 13 (FIG. 1),stab-in anchors 12 (FIG. 1) and conduit clamp arms (not shown). The DFCSis deployed to the sea bed on a deployment frame 15 (FIG. 2) which canbe raised or lowered from a support vessel (not shown) moored above theconduits C to be joined.

2.2 AXIAL FORCE TOOL

The Axial Force Tool (AFT) 20, shown in detail in FIG. 4, is primarily asteel structure designed to perform close proximity tie-ins. It is usedin conjunction with the Reaction Tool (RT) 30 (FIG. 5) arid other itemsof the connection equipment to perform pull-in operations and flangealignment. The AFT can also be used for flexible line pull-in using aflange puller system with the possibility to increase, on demand, theavailable length of pulling wire.

The AFT comprises of a steel structure 21 (FIG. 4) manufactured eitherfrom commercially available standard or high strength steel. Thestructure includes two main lateral members, and a combination ofsmaller members to stiffen the structure In one configuration allmembers are tubular, some of which can be flooded and others which canbe kept free of water to give additional buoyancy when submerged toreduce in water weight

Mounted onto the structure are two hydraulically operated clamp modules22 (FIG. 4), front and rear The clamp modules 22 serve two functions;they allow the AFT to be installed onto the conduit securely by means ofclamp cylinders 25, and they allow the conduit to be deflected relativeto the AFT structure.

The front and rear clamp modules 22 are manufactured to suit a range ofconduit size. Each clamp module will comprise of four cylinders 25 (FIG.4) fitted to each of the front and rear clamp modules. Clamping onto theconduit is via parallel control of the front and rear clamp cylinders25.

The use of a hydraulic accumulator (not shown) could also allow the ROVto leave the AFT to install the docking anchors 23 (FIG. 4) in the RTreceptacles 34 (FIG. 5) should a second ROV be unavailable. In anemergency, the pipe clamps cylinders are released and allow the AFT tobe recovered.

Also mounted onto the main structure is a wire rope type flange pullingsystem 23 & 26 (FIG. 4), referred to as the pull-in system Thiscomprises of two flange pulling cylinders 26 (FIG. 4), one each fittedto the port and starboard sides at the front of the AFT frame. Thepull-in system 23, 26 is used to provide the capability of theconnection system to draw the flanges of the conduit together.Alternatively, the pull-in system could be replaced by standard subseawinches or hydraulic cylinders.

The pull-in system 23, 26 will employ existing commercially availableflange pulling technology, but adapted to suit the specific needs of ROVoperation. Each flange pulling cylinder 26 (FIG. 4) is essentially alinear winch which pulls in a length of rope on each stroke.

The main AFT structure is also fitted with a frame engagement system 24(FIG. 4) which permits the AFT to engage and lock to the RT structure,so forming a single structure used for the conduit deflection Operation.

Contained within the AFT is a hydraulic system that provides the meansof power to the pull-in system, clamp modules, frame engagement system24 and clamp module deflection. Hydraulic supply for the AFT will beprovided by the Interface Skid 50 (FIG. 7) which is carried under thehost ROV. The AFT will be fitted with two interconnected hydraulicsystems: one medium pressure, and one high pressure. The medium pressuresystem will be used but not limited to control pipe clamps, clamp modulevertical motion and frame engagement and lock functions. The highpressure system will be used but not limited to provide control of clampmodule 22 horizontal motion (pipe/spool-piece deflection) and control ofthe pull-in system (pipe/spoolpiece pull-in) 23, 26.

The AFT is to contain many “failsafe” features which allow recovery ofequipment with minimal damage if a failure (hydraulic or mechanical)occur during operations The loads being transmitted to the conduit arealso to be monitored to ensure no damage occurs.

2.3 REACTION TOOL AND REACTION YOKE

The Reaction Tool (RT) 30 (FIG. 5) and Reaction Tool Yoke (RTY) 31 (FIG.5a), are primarily steel structures designed to assist tie-in operationsby reacting all forces applied by the Axial Force Tool (AFT) 20 (FIG.4). They are used in conjunction with the AFT and other items of theequipment spread to perform pull-in operations and flange alignment.

The RTY is used instead of the RT on conduits where installation spaceto allow connection is limited (i.e. 1st end tie-in to a subseastructure). In certain applications. the possibility of having a limitedspace behind the connection point is possible (this applies, forexample, in case of a riser with a gooseneck termination, a manifoldflange. etc.). In these instances the alignment loads are reduced.

The RT comprises of a steel structure 32 (FIG. 5) manufactured fromeither commercially available standard or high strength steel. The samephilosophy as for the AFT has been adopted

Mounted onto the structure are two hydraulically operated clamp modules33 (FIG. 5), front and rear

The clamp modules 33 allow the RT to be installed the conduit securelyby means of clamp cylinders 36 (FIG. 5) The clamp cylinders 36 areincluded in a structural frame 32 (FIG. 5) designed to pass all loadsdue to deflection of the spoolpiece or flowline (axial force, lateralcomponent and torsion) back into the conduit. This is achieved by theuse of high force clamp cylinders 36 which “grip” the tool to theconduit—the structural frame 32 being used to avoid loads other thanpush/pull acting on the clamp cylinders.

In a similar manner to the AFT, the RT is provided with a means ofaccommodating different conduit sizes by the fitting of different sizeclamp modules 33.

Mounted onto the front of the RT structure 32 (FIG. 5) are receptacles34 (FIG. 5) for anchoring the wire ropes of the AFT pull-in system 23,26.

The RT structure 32 is also fitted with a frame engagement system 35(FIG. 5) which permits the RT structure to engage with the AFT structure28, so forming a single entity used for deflection of the conduit.

Contained within the RT is a hydraulic system which provides the meansof power to the front and rear clamp modules. The RT will be fitted witha dual port female stab (not shown) to provide control of hydraulicservices Hydraulic supply for the RT will be provided by the interfaceskid 50 (FIG. 7), which is carried the host ROV. The RT will be fitted ahydraulic system. The hydraulic system will be used but not limited toclamp the clamp modules 33 onto the conduit and provide the clampingforce necessary during deflection of the conduit.

The RT yoke 3 (FIG. 5a) is essentially a reduced length RT with only oneclamp module fitted 33 (FIG. 5a). Clamp module size is as for RT

2.4 FLANGE CONNECTION TOOL

The Flange Connection Tooling (FCT) system comprises a suite of toolswhose purpose it is to effect a bolted flange connection and consists ofthe Bolt Insertion and Tensioning Tool (BITT) 46 (FIG. 6a) and the NutMagazine Tool (NM) 41 (FIG. 6). The tools are deployed eitherpre-installed on the conduit, sub-sea deployed by ROV manipulator, orflown into position by the ROV, depending on the size of the conduit.

Part of the FCT system is a Nut Magazine 41 (FIG. 6) which isconstructed in two hinged half housings 44 (FIG. 6) containing the fillquantity of nuts 41a required to connect the flanges. The two halfhousings 44 are hinged about the conduit centre-line which allows thehalf housings to be closed around the conduit.

There are two methods for deploying the NM 41 onto the conduit. The NutMagazine 41 is placed over the conduit (at the Reaction Tool side) bythe ROV using the ROV manipulator with a ‘T’ bar handle attached to thetool (for pipelines 4″ to 10″). Alternatively, for conduits of 12″ andabove, the is flown directly onto the conduit by the ROV using a dockingpoint 42 (FIG. 6). The half housings 44 (FIG. 6) can then be closed tolock the magazine around the conduit

The Reaction Tool 30 (space permitting) or Reaction Tool Yoke 31 isemployed to retain the magazine 41 axially and locate it at the rear ofthe conduit fixed flange.

Each nut 41 a is held within a machined toothed sprocket. The sprocketsare driven round by the operation of hydraulic motors, thus rotating thenuts to engage with the studs when they are introduced.

Hydraulic fluid is supplied to the motors by an ROV dual port hot stab43 (FIG. 6). The hot stab receptacle is mounted near the docking point.

Rotary alignment of the magazine 41 to align each nut with therespective bolt hole, is achieved by the engagement of two guide pinsfrom the Bolt insertion and Tensioning Tool (BITT) 45 (FIG. 6a) intoholes machined into the Nut Magazine body. A tapered lead-in cone 40(FIG. 6) is added to ease the engagement of the pins.

Solid buoyancy blocks are attached to sides of the magazine to reducethe in water weight of the tool and enable ROV handling

Another part of the FCT system the Bolt Insertion and Tensioning Tool(BITT) 45 (FIG. 6a). This contains a magazine 46 of retained bolts 46 a(FIG. 6a), referred to as the bolt magazine. The bolts are to beinserted through the conduit flanges as part of the flange connectionoperation. The magazine 46 also contains a quantity of stud tensionerunits, which act upon the back of the studs during the bolt tensionoperation and into which the bolts are loaded before deployment.

The magazine is fixed within a surrounding deployment structure whichprovides clamp, rotation and extend hydraulic functions.

The BITT structure 47 (FIG. 6a) is constructed of a series of horseshoeshaped plates 47 a which locate over the conduit flange. The plates areconnected by slide tubes (which run from the rear plate to the frontplate) and two linear, hydraulic cylinders.

The magazine is contained within two central horseshoe plates 47 c.These two plates are fixed together by bearing housings which guide theunit along the slide tubes 47 b.

The magazine 46 is constructed in two hinged half housings 46 acontaining (if space permits) 100% coverage of stud tensioners The twohalves are pivoted to open and close around the pipe by two hydraulicclamp cylinders 48 (FIG. 6a) .

The rear horseshoe plate of the BITT 45 locates against the AFT 20 (FIG.4) which provides an axial reaction to the forward movement of the boltmagazine 46. The AFT 20 also provides a key which the horseshoe platelocates with to provide a reaction to rotational movement, Mounted atthe rear of the BITT is a hydraulic cylinder which rotates the BITTstructure 47 relative to the conduit. This aligns the bolts 46 acontained in the BITT bolt magazine 46 with the bolt holes of the swivelflange located on the conduit. This cylinder is also capable of rotatingthe tool together with the swivel flange to align the bolts to the boltholes of the fixed flange on the mating conduit.

The tensioner units (not shown) are made up of three parts, theload-bridge, the tensioner jack and the reaction nut.

For this application (ROV operated) the forward mounted load-bridgeincorporates a motor gear drive to rotate the nut down the stud duringtensioning. Each nut 41 a is held within a machined toothed sprocket.Each sprocket is driven round by the operation of a hydraulic motor,thus rotating the nuts.

The tensioner jack is a conventional unit which has pressure intensifiedhydraulic fluid supplied to an annulus of the correct area to providesufficient tension to the bolt 46 a.

At the rear of the tensioner jack is the reaction nut. The reaction nutis a split collet which has a thread profile machined on its insidediameter. The reaction nut can be opened and closed around the threadedstud by the actuation of a small linear hydraulic cylinder or theoperation of a hydraulic motor. This grips the stud and provides thereaction to the tensioner jack.

If it is not possible to achieve 100% coverage of the flange bolts withthe tensioner units then the magazine will be divided into two parts Apart which retains the 100% bolts, the bolt magazine 46, and a partwhich contains the 50% tensioner units, the tensioner magazine 46 t. Thebolt magazine shall operate as previously described, however thetensioner magazine requires a forward/aft movement and a rotationmovement. These functions will be incorporated into the existingstructure by the addition of slide tubes, bearing housings, and mountingplates, similar to those described above but with smaller strokes.

The BITT 45 tool contains an integrated control system based around ahydraulic valve manifold 49 (FIG. 6a) . The manifold 49 will have abuilt-in facility to accommodate cameras and lighting on the tool Powerto the manifold will be via a composite electrical/hydraulic hot stabconnector deployed from the tooling skid using a manipulator ann.

The tool is deployed/removed from the conduit by the ROV utilising adocking point.

Solid buoyancy blocks are attached to the structure of the tool toreduce the in water weight and enable ROV handling after the bolts havebeen released from the tool.

2.5 Tooling Skid

To allow the ROV to interface with the AFT 20, RT 30, and FCT 40, andprovide hydraulic and electrical power to them, a tooling Interface Skid50 (FIG. 7), is necessary. The interface skid will also allow isolationof the AFT, RT and FCT hydraulic systems from the host ROV, thuspreventing any contamination of the host ROV hydraulic system leading tooperational complications and failure.

The skid 50 will comprise of an aluminium structure 51 (FIG. 7),containing an isolated hydraulic system 52 (FIG. 7), mechanicalinterface points 53 (FIG. 7) and buoyancy.

The skid 50 structure is designed to allow the ROV to interface witheither the AFT, RT or FCT by means of mechanical docking probes 53 (FIG.7).

Electrical and hydraulic connections will be made between the ROV andthe T and the FCT via a sub-sea stab connector 54 (FIG. 7), located onthe interface skid 50. This will pass hydraulic power, electrical powerand command signals from the ROV to the AFT tooling manifold.

The skid 50 is also fitted with a dual port stab 55 (FIG. 7) to allow aswitch-able hydraulic supply to be available for the RT and thelightweight H-frames.

Control of the mechanical docking probes and electro-hydraulic stabconnector 54 is hydraulic from the ROV. Fail-safe systems installed onthe skid will allow the ROV/skid to disengage from either tool afterloss of hydraulic power.

Buoyancy will be contained within the skid structure to provide the skid50 with a neutral in-water weight.

The skid 50 mechanically attached to the ROV and is used as an interfacebetween the ROV and the tool. The skid independent hydraulic system isswitched on by a pilot hydraulic signal from the ROV. This then makeshydraulic power available at the electro-hydraulic and dual port stabs54, 55 on the skid 50.

Electrical power from the ROV is passed directly to the tool via theelectro-hydraulic stab 54. Control of the tooling manifold on the AFT isthen possible via electrical command signals from the ROV.

Hydraulic power on the skid 50 can be switched between automatedelectro-hydraulic stab, articulated arm deployed electro-hydraulic stab54 articulated arm deployed hydraulic dual-port stabs 55 or acombination.

The tooling skid is fitted with a mechanical interface point at thefront to allow the ROV to lock on to and pick-up either the connectionequipment tools. The skid may also be fitted with vertical attachmentpoints to reduce the loading on the front interface point.

2.6 OPERATIONS SUPPORT EQUIPMENT

Additional equipment is required to support the connection systemoperations, these include a Lightweight H-frame (LHF) 60 (FIG. 8), apipeline Metrology System (not shown), a Seal Insertion and Removal Tool(SIRT) 65 (FIG. 9) and 66 (FIG. 9), a Blind Flange Removal Tool (BERT)67 (FIG. 10), a Pig Launcher Removal Tool (PLRT), a Flange Spreader Tool(FST) (not shown), a Spoolpiece Installation Guide Tool (SIGT) 68 (FIG.10), a Flange Cleaning Tool (FCT) (not shown), a Sub-sea Winch 69 (FIG.11), and finally a Dead Man Anchor (not shown), each of which will bedescribed in greater detail below.

2.6.1 H-FRAME

The Lightweight H-frame (LHF) 60 (FIG. 8), is an ROV deployed andoperated tool, designed to lift and position rigid flowlines duringtie-in operations. The system is of a low weight/low force, whichguarantees its installation and operation by a standard work class ROV.

The H -Frame 60 can operate at up to 2500 m water depth. i.e. alloperations are performed without any diver assistance. It can also beeasily adapted as each field will have its own specific requirements.

H-frames are generally used in pairs.

The LHF 60 is an aluminium structure composed of two foundations pads 61(FIG. 8), two vertical legs 62 (FIG. 8), a connection frame 63 (FIG. 8)and a clamp 64 (FIG. 8).

The foundation pads 61 (FIG. 8) are designed to have stability in softsoil with low shear strength. However, in case a lower bearing capacitysoil is found, by replacing the feet almost all soil types can beaccommodated. The pads may also include two water injection hot-stabs toallow separation of the mud mats from the pads

The two legs 62 (FIG. 8) can be extended in order to pick up a pipeburied 250 mm in the seabed and hold it up to 750 mm from the seabed andthe clamp can be translated+/−500 mm with respect to the centre line ofthe structure.

The clamp 64 (FIG. 8) is a scissors type, hydraulically operated by asingle acting cylinder. The jaws of the clamp are able to grab and lifta partially buried rigid pipeline. Through additional spacers, the sameset of jaws can cope with different pipe sizes.

Dual port hydraulic hot stabs are provided on the LHF to allow the ROVto control the clamping, horizontal and vertical translation functions.

As the primary option, the LHF will be designed to be fully ROVdeployable This will require a mechanical interface to allow the ROV todock onto the LHF and sufficient buoyancy modules (syntactic foam) willbe required to maintain the tool with a slightly negative in waterweight.

2.6.2 METROLOGY SYSTEM

The Metrology System (not shown) can be one of two systems commerciallyavailable for subsea use with an ROy, there are either an AcousticMetrology System or a Taut Wire Metrology System.

The Acoustic Metrology System consists of an ROV carried skid/frame thathas mechanical interfaces on the front end, a pipeline engagementprofile at the bottom and the acoustic metrology survey systems mountedwithin it. The acoustic equipment is primarily: a survey for measurementof orientation, relative to magnetic north; a USBL transponder, forpositional measurement relative to the transponder array; and a depthtransducer for accurate relative depth measurement.

All survey I metrology signal data from the systems on the skid is sentto the surface via the ROY umbilical.

The Taut Wire metrology system is a purely mechanical system that relieson protractors at the attached end points i.e. the two flanges orsuitable steelwork attached to the blind flange and/or pig launcher, forvisual measurement of relative angles.

The distance between the flanges is measured by a mechanical odometersystem that measures wire as it is paid out when the ROY flies theconnecting wire from one flange to the other.

2.6.3 SEAL INSERTION AND REMOVAL TOOL

The Seal Insertion Tool (SIT) 65 (FIG. 9), is deployed by the ROVmanipulator in a carrier fitted with an ROV T-bar handle. The seal issuspended in a support structure and located Onto the ends of thepartially exposed bolt heads. Once the flange bolts are fully insertedthe insertion tool may be removed.

The Seal Removal Tool (SRT) 66 (FIG. 9), is a contingency tool in theevent that the face seal does not come away with the blind flange andremains attached in the groove of the weld-neck flange.

The tool will have a cylindrical body with a conical lead-in profile andwill be inserted by ROV manipulator into the weld-neck flange. A pair oflocking shoes will be actuated by hydraulic cylinder to “friction grip”the inside of the seal ring. The seal assembly can then be jacked offthe sealing face without damage to the face.

2.6.4 BLIND FLANGE REMOVAL TOOL

The Blind Flange Removal Tool (BFRT) 67 (FIG. 10), shown in detail inFIG. 10, is an ROV operated tool, designed to cut the studs. and nuts ona blind flange to enable removal. The is divided in three parts. thelocking system; the stud cutting system; and the nut cutting system

The locking system is a docking nose which is positioned in the flangeinterface and locks in with four dogs hydraulically operated The surfacein contact is knurled to provide a better grip. The flange interface isa simple cylinder with an internal diameter to suit the BFRT nose, witha guiding cone entrance.

On the locking system is mounted a rotary actuator to allow 180 degreerotation of the cutting tools composed of two horizontal, hydraulicmotor driven grinding discs mounted both sides of the rotary actuator,which cuts the studs above the nuts.

2.6.5 PIG LAUNCHER REMOVAL TOOL

The pig launcher removal tool (not shown) is a traditional ROV operatedtorque tool. Due to the reduced pressures during pigging operation, thepig launcher bolts will not be tensioned and can be removed usingstandard tooling.

2.6.6 FLANGE SPREADER TOOL

The flange spreader tool (not shown) is a contingency tool in the eventthat it is, not possible to remove the pig launcher or blind flange oncethe flange fixing bolts I nuts have been removed.

The flange spreader tool will consist of a steel framework which isdeployed over the flange joint. Within the frame is contained a pair ofcommercially available flange spreading tools which can be extendedforward to engage in the flange joint. The tools are then operated inthe conventional manner by extending a chisel head into the joint toeffect separation.

26.7 SPOOLPIECE INSTALLATION GUIDE TOOL

The Spoolpiece Installation Guide Tool (SIGT) 68 (FIG. 10), also acts asprotection for the pre-installed flange face seal.

The SIGT consists of two mating parts: the male guide; and the femalereceptacle.

The male guide consists of an ROV deployable pipe clamp fitted with aconventional guide post. The clamp is deployed onto the pipeline priorto installation of the spoolpiece by the ROV and activated through ahydraulic hot stab. An accumulator maintains the clamp in position andthe ROV can leave the area whilst the spoolpiece is deployed

The female receptacle is installed on the spoolpiece mating flangediameter prior to deployment of the spoolpiece and also acts as a flangeseal face protector. The guide is held in place by a clamp which ismaintained by an accumulator. During spoolpiece deployment the ROYmonitors and guides the female receptacle into position on the maleguide post.

Once deployment of the spoolpiece is complete, the female guidereceptacle is opened and removed by the ROV. The male guide can thenalso be removed by the ROY. Both items are removed to the toolingbasket.

2.6.8 FLANGE CLEANING TOOL

The Flange Cleaning Tool (not shown) is a hydraulically operatedrotating brush in conjunction with a LP Water jet system. The brush ismade up from soft scouring pads several layers thick, secured to acentral spindle protected to prevent ‘metal to metal’ contact on theflange face and seal area.

The brush may be required to be changed out due to wear on prolongedcleaning sections

The brush is mounted on to a small, high speed hydraulic motor with aT-Bar suitable for manipulator operation. Incorporated into the T-bar isa bracket for mounting a camera and light unit to give ‘close-up’ PreClean inspection, continuous monitoring during Flange Face Cleaning andPost cleaning inspection.

A LP Water Jet is used to remove light debris and mud from the flangeface and for final clean-up before the post cleaning inspection.

An option on the rotating brush unit is a HP water jet system to cleanthe Flange Face set to a level safe for the Flange material preventingany possibility of damage.

2.6.9 SUBSEA UTILITY WINCH

The Sub-Sea Utility Winch 70 (FIG. 11), is an ROV operated hydraulicwinch mounted on a swivel frame on a clump weight base. It will be usedto aid the positioning of the rigid flow-line and spool-piece from 4″ ODup to 24″ OD during tie in operations. The sub-sea winch can operate at2500 metre water depth. i.e. all operations are performed without anydiver assistance.

The Sub-sea winch consists of a base frame, winch support frameturntable (3600) and a hydraulic winch system.

The Base frame is designed to keep the winch in position during pull inof the winch wire rope. The base frame consists of a steel frame with aconcrete in-fill. It also has four lift points for easy deployment.

The winch support frame can rotate 360° horizontally to allow alignment.This includes cable storage bull horns that allows the winch wire ropeto be free pulled out from the winch without hydraulic actuation Thesupport frame is constructed from steel.

The sub-sea winch system consists of a hydraulic motor connected to thewire rope drum via a gearbox and hydraulic brake. The winch has a linefeed in/out measurement system in the form of a turns counter.

For docking with the ROV a docking cone and a dual port hot-stabreceptacle are located on the top of the structure. The dual porthot-stab hydraulically actuates the winch in and out operations of thesub-sea winch using the ROV.

2.6.10 DEAD MAN ANCHOR

The dead man anchor (not shown) or bollard clump weight as it issometimes called, is essentially a steel frame/concrete in-fill gravityanchor with a bollard centrally mounted. It is a passive structure andprovides a reaction point for pulling operations sub-sea, such aspulling the pig launcher away from the flow-line or coarse alignment ofthe spool-piece.

3. PROCEDURE FOR CONNECTING A RIGID CONDUIT TO A FLEXIBLE CONDUIT

Referring now to a first embodiment of the method of connectingunderwater conduits together, shown in FIGS. 12, 13 and 14, a flexibleconduit C, fitted with a suitable DECS interface collar 16 (FIG. 12) islaid down on the seabed 100 (FIG. 12) within a target area. A LHF 60(FIG. 12) is deployed and clamped to the flexible conduit C′ inaccordance with known techniques. The LHF 60 (FIG. 12) is launched froma support vessel moored above the connection site. The interface collar16 (FIG. 12) allows the DFCS 10 (FIG. 12) described above to be lockedon to the flexible conduit C′.

The RT 30 (FIG. 12) is located on its deployment frame. The DFCS 10(FIG. 12) is located on its deployment frame 15 (FIG. 12) together witha torque tool, seal ring replacement tool and spare connector seal (notshown).

Depending on the size of the conduit C and on the height of theconnector 75 (FIG. 12) from the seabed 100 (FIG. 12). buoyancy modules85 (FIG. 12) may be installed on the second conduit C′. The saidbuoyancy modules can be inflated from a single air source, located onthe sea bed, and operated by the remotely operated vehicle.

A Remotely Operated Vehicle (ROV) 80 (FIG. 12) is launched to the worksite from the support vessel and performs a survey of the said worksite. Information retrieved from the survey is fed back to the supportvessel so that the appropriate parameters for the connection can bedetermined. The remotely operated vehicle is provided with anarticulated manipulation arm 81 (FIG. 12) which allows the remotelyoperated vehicle to pick up selected objects.

The ROV 80 (FIG. 12) docks onto the LI-IF 60 (FIG. 12) and places theframe in position around the free end of the first conduit C. The ROVthen operates the clamp 64 (FIG. 8) of the frame which grabs and holdsthe rigid conduit C in position.

The ROV is disconnected from the LHF 60 (FIG. 12) and positioned toretrieve the RT 30 (FIG. 12) from its deployment frame and carry the RT30 (FIG. 12) to a position above the conduit C. The RT 30 (FIG. 13) isthen lowered onto the conduit C. The clamp module 33 (FIG. 5) of the RTare activated in order to lock the RT in position on the conduit C.

The ROV is then operated to remove the protection cap from the saidrigid conduit C.

The ROV then docks onto the DFCS 10 (FIG. 13) to make up itselectro-hydraulic connector. The conduit clamp arms of the DFCS are thenopened to enable the DECS to be retrieved from the deployment frame.

The ROV is then positioned adjacent the RT 30 (FIG. 13) and movesforward to dock the anchors 12 (FIG. 1) of the DFCS into the receptacles34 (FIG. 5) of the RT. This action anchors the ends of the two DFCSwinches 13 (FIG. 1) to the RT 30.

In FIG. 13 the ROV activates the DFCS winches 13 (FIG. 1) to pay Outwinch ropes 14 (FIG. 13) and, at the same time moves back to a positionabove the interface collar 16 (FIG. 13) of the flexible conduit C′ TheROV then lowers the DECS 10 (FIG. 13) onto the second conduit C′, overthe interface collar 75 (FIG. 14) and activates the conduit clamp arms.This pulls the flexible conduit out of the sand/mud at the sea bed andlocks the DFCS 10 (FIG. 14) to it.

Mechanical indicators (not shown) provide a means to verify that theDFCS 10 (FIG. 10) is securely engaged over the axial load reaction shearkeys of the interface collar 16(FIG. 10).

The DFCS winches 13 (FIG. 1) are activated to commence pulling of theflexible conduit C′ up to the rigid conduit C. The winch rope tensionersare monitored during this operation to allow for adjustment ifnecessary. If the conduit C′ is not horizontally aligned on the seabed100 (FIG. 14) when the two conduits are close together and the hub (notshown) arrives at the connector 75 (FIG. 14), a sub-sea utility winch 70(FIG. 11) may be used to pull the conduit C′ into position using astandard procedure.

The said sub-sea utility winch 70 (FIG. 11) is deployed on the seabedfrom the surface support vessel, whereby the ROV can connect the wirerope from the said winch directly or via a Dead Man Anchor to the saidflexible conduit. Once connected it can perform the following twofunctions; pull the conduit towards the sub-sea utility winch; then lockin place the position of the conduit after pulling.

The winch on the sub-sea utility winch is actuated by a dual porthot-stab from the ROV that powers the hydraulic motor on the winch. Ifnecessary the direction of the force being applied can deflected usingthe said Dead Man Anchor until the alignment of the free ends of theconduits has been corrected. The method of locking the wire rope inposition is by the use of a braking system on the winch wire drum.

If required, the final vertical alignment of the conduit C′ may beachieved by adjusting the position of the buoyancy modules 85 (FIG. 14)along its length.

The DFCS 10 (FIG. 14) continues to pull the said flexible conduit C′ upto the said rigid conduit termination until the two are a defineddistance apart. In FIG. 14 the conduit hub (not shown) is drawn into theconnector 75 (FIG. 14).

The flexible conduit protection cap is removed from the end of the saidflexible conduit C′ by the ROV manipulator arm 81 (FIG. 14).

The said DFCS winches 13 (FIG. 1) continue to operate until the saidflexible conduit hub is at a certain distance from the said rigidconduit hub. The final part of the pull-in is then performed using thesaid DFCS winches with the said DFCS slide tubes arresting the motion.This provides a controlled method of aligning the two as the finaldistance is made up. Visual confirmation is made with the ROV cameras.

The said ROV makes up the connection, the connector being a clampconnector, a collett connector, a bolted flange connector or any othersuitable connection device.

An air hot stab is taken from the above mentioned seal ring test system(located on the ROV) and is inserted into a receptacle on the matedassembly. The said air hot stab is pressurised and the pressuremonitored. This provides an external seal test verify the integrity ofthe seal between the two conduits.

If the pressure test fails, the joint is opened and the said flexibleconduit retracted by hydraulically extending the said DFCS slide tubes.The ROV retrieves the seal ring replacement tool from the said DFCSdeployment frame and uses it to remove the seal and replace it with anew one. The said flexible conduit is again pulled up and the procedurerepeated until the seal test result is satisfactory.

Once a successful seal test has been completed the said DFCS disconnectsthe stab-in anchors from the said RT receptacles and unclasps and thesaid DFCS 10 (FIG. 1) from the said flexible conduit C′. The DFCS andsaid tools are returned to the respective deployment frames which arethen ready for recovery to the surface.

The ROV docks onto the said RT 30 (FIG. 14) and removes it from therigid conduit C and returns it to its deployment frame which is thenready for recovery to the surface.

The ROV releases the completed conduit assembly by releasing the clampmeans 64 (FIG. 8) of the said LHF 60 (FIG. 14) which is then ready forrecovery to the surface, additionally the ROy then deflates and recoversany buoyancy modules 85 (FIG. 14) which have been used.

FIG. 14 also shows the recovery to the surface of DFCS 10, RT 30 and therecovery to the surface of the LHF.

FIGS. 15 and 16 show the connection procedure to connect a flexibleconduit to a subsea structure (xmas tree) using the DFCS.

The method outlined above describes the connection of the rigid conduitC to a flexible conduit C′ However, in accordance with a secondembodiment of the invention, a rigid conduit C may be connected toanother rigid conduit C″ and the respective steps of this alternativemethod are described below. Similar components from the first method aredescribed below Similar components from the first method have been giventhe same reference numerals for ease of understanding.

4. PROCEDURE FOR CONNECTING A RIGID CONDUIT A RIGID CONDUIT

Referring now to a second embodiment of the method of connectingunderwater conduits together, in FIGS. 17 to 21 a rigid conduit C isconnected to another rigid conduit by the inclusion of a rigidspoolpiece C+ (FIG. 17)

The two rigid conduits C and C″ (FIG. 17) are laid on the seabed inaccordance with known techniques (one of the conduits could be part ofan underwater structure such as a flowline bases, a x-mas trees, atemplate or similar)

As shown in FIG. 12 the ROV 80 is launched to the worksite from thesurface support vessel and performs a site survey sending informationback to the support vessel for analysis. The ROV will locate and removeany significant debris, and dredge any problem areas around the conduitflanges for access.

The chosen metrology equipment is launched to the seabed within adeployment basket or onboard the ROV. The ROV will then operate saidmetrology equipment to relay conduit flange position information back tothe support vessel for analysis From this information a rigid spoolpieceC+ is fabricated onboard the support vessel to fit between the two rigidconduits.

Operations support equipment is launched to the seabed from the supportvessel. The type of support equipment required will depend upon fieldlayout and hardware employed by field constructors. As a minimum twoLHF's 60 (FIG. 8), a sub-sea utility winch 70 (FIG. 11) and a dead mananchor are required.

The LHF's are deployed on the seabed by the vessel crane, whereby theclamp is then located straddling the conduit using the ROy. Once inposition the LHF can perform the following two functions; clamp onto therigid conduit with the lifting clamp 64 (FIG. 8); apply a horizontal andvertical movement to allow rough positioning of the rigid conduit.

The LHIF clamp 64 (FIG. 8) is actuated by a hydraulic cylinder(activated by a hotstab from the ROV) that applies a 5 Tonne force toclamp securely onto the rigid conduit. The horizontal positioning of therigid conduit is achieved by the use of two horizontally mountedhydraulic cylinders. These, in turn, move a sliding collar which isattached to the lifting clamp The vertical positioning of the rigidconduit is achieved by the use of two vertically mounted hydrauliccylinders 62. These are attached to feet 6] (FIG. 8) which react againstthe seabed

Further preparation work may take place at this stage, as shown in FIG.18. i.e removal of the 1st end rigid conduit C flange protection cap orblind flange using the Blind Flange Removal Tool (BFRT) 67 (FIG. 10),removal of old seal using the Seal Removal Tool (SRT) 66 (FIG. 9), sealface cleaning using the Flange Cleaning Tool (FCT), installation of theSpoolpiece Installation Guide Tool (SIGT) 68 (FIG. 10), and removal of aPig Launcher (if fitted) from the end of conduit C+.

The said rigid spoolpiece C+ is laid on the seabed within a specifiedtarget area within the pull-in capabilities of the connection apparatus,as shown in FIG. 19. If the said SIGT 68 (FIG. 10) is employed, then theROy will be used to guide the spoolpiece so that the female receptacleof the SIGT on the spoolpiece C+ locates with the guidepost on the rigidconduit C.

The ROV is recovered to the surface support vessel to fit the InterfaceSkid 50 (FIG. 7) to the underside of the ROV structure and connect it'shydraulic and electrical system with that of the SKID 50 (FIG. 7). Oncecomplete the ROV is once again launched to the seabed.

The Reaction Tool (RT) 30 (FIG. 5) or the Reaction Tool Yoke (RTY) 31(FIG. 5a) (dependant on field layout), the Axial Force Tool (AFT) 20(FIG. 4) and the Flange Connection Tooling (ECT) (FIG. 6 and 6a)(dependant on flange connector type) are deployed to the seabed from thesurface support vessel. All units are contained within their respectivedeployment structures.

The RT 30 (FIG. 5) or RTY 31 (FIG. 5a) are passive structures designedto interface with the AFT and transmit the spool alignment forces fromthe AFT into the conduit To enable the RT or RTY to provide thisreaction path, it is deployed by the ROV onto rigid conduit C, and isclamped using a friction clamp 33 (FIG. 5) onto the conduit.

This is achieved as the ROV moves to the RT 30 (FIG. 5) and docks on toit's mechanical interface, and makes up it's hydraulic hot stabconnector to provide the friction clamp 33 (FIG. 5) with hydraulicpower. The RT clamps are opened to remove it from it's deployment frame,from where it is flown by the ROV into position on the rigid conduit C.Once the RT has been deployed in the correct location, it is clampedonto the conduit, no further operations are carried out form the RT. TheRT is left installed on the conduit with an accumulator and check valvesystem to maintain a constant clamping pressure as farther operationsare performed.

The following procedural steps are shown in FIGS. 17, 18, 19, 20 and 21,and the connection apparatus operation is shown in more detail in FIGS.22 to 25

After installation of the RT, the ROV moves to the AFT 20 (FIG. 18) anddocks on to the mechanical interface, and makes up the electro-hydraulicconnector 54 (FIG. 7) to provide the clamp module 22 (FIG. 4) withhydraulic power. The AFT clamps are opened to remove it from it'sdeployment frame, from where it is flown by the ROV into position on therigid spoolpiece C+ Once the AFT ‘has been deployed in the correctlocation, it is clamped onto the pipeline using two hydraulicallyoperated pipe clamps, front and rear. The AFT is left installed on theconduit with an accumulator and check valve system to maintain aconstant clamping pressure as further operations are performed.

The ROV then disengages from the AFT and using it's articulated armremoves the SIGT 68 (FIG. 10) from the flanges of both the rigidspoolpiece C+ and the rigid conduit C. and helps recover them to thesurface support vessel.

Again using it's articulated arm, the ROV removes the flange pull-inwire anchors 23 (FIG. 4) from the AFT and secures them into thecorresponding RT anchor receptacles 34 (FIG. 5).

The ROV once more docks into the mechanical interface of the AFT andmakes up the electro-hydraulic connector to provide the pull-in systemwith hydraulic power. Pull-in of the rigid spoolpiece C+ towards therigid conduit C is achieved by the hydraulic operation of the pull-insystem installed on the AFT. Port side and starboard side pull-in wirescan be individually controlled.

As the AFT is pulled towards the RT, the clamping modules 22 (FIG. 4) ofthe AFT are free to float within the AFT structure. This allows the AFTand RT frames to attain alignment given that both the RT and AFT areclamped onto the rigid pipeline C and the rigid spool-piece C+respectively,

As the AFT and RT are drawn towards each other, guides 35 (FIG. 5) atthe front of the structures engage and ensure that the AFT and RTstructure align with each other.

When the AFT and RT structures are fully docked, hydraulic locking pins24 (FIG. 4) located on the AFT are engaged, so connecting the AFT and RTas one structure.

During pull-in the misalignment between the pipeline flange andspool-piece flange will remain, the clamping modules within the AFT willfloat in the horizontal and vertical planes to compensate for themisalignment.

Once locking of the AFT and RT structure has taken place and the AFTclamping carriages have been misplaced due to the flange misalignment,final alignment of the spool-piece will take place.

This is achieved by operation of the AFT clamping module horizontal andvertical deflection cylinders. Operation of these cylinders allows thespool-piece to be deflected back onto the centreline of the AFTstructure and hence in alignment with the RT structure and consequentlythe mating flange

The rigid conduit flanges are now ready for connection, as shown in FIG.23, the connector being a clamp connector, a collet connector, a boltedflange or any other type of suitable connection device.

The following describes a method for the connection of standard boltedflanges, and is shown in detail in FIG. 24, where the flange on rigidconduit C is a fixed type, and the flange on rigid spoolpiece C+ is of aswivel type, using the previously described FCT 40 (FIG. 6).

The ROV disconnects from the AFT and docks into the mechanical interfaceof the BITT 45 (FIG. 6a) and makes up it's electro-hydraulic connectorto provide the BITT with power. The BITT clamps are opened to remove itfrom its deployment frame, from where it is flown by the ROV intoposition on the rigid spoolpiece C+. Once the BITT has been deployed inthe correct location (in between the AFT structure and the spoolpiece C+flange), it is clamped to the spoolpiece with the bolts facing theswivel flange.

Connection of the flange is now ready to proceed as follows:

By providing hydraulic power to the BITT the bolts are to be extendedthrough the spoolpiece C+ flange bolt holes until protruding from theflange face.

ROV to disconnect from the BITT and retrieve the Nut Magazine (NM)41(FIG. 6) from the deployment frame and clamp it in position around therigid conduit C (in between the RT structure and the pipe flange)

ROV to retrieve and deploy the seal carrier c/w seal and locate in thespoolpiece C+ flange face using the bolts as a guide.

ROV to connect with the BITT once more to rotationally align the boltsc/w the spoolpiece swivel flange with the pipe fixed flange holes, byhydraulically rotating the BITT structure 47 (FIG. 6a)

Alignment pins are to be hydraulically extended from the BITT and locatewith receptacles in the NM to bring the NM and it's contained nuts intoalignment with the flange holes

The bolts are then extended further through the aligned fixed flange andlocate with the nuts contained within the NM.

The NM hydraulic motors are operated by a hydraulic hot stab 43 (FIG. 6)from the ROV articulated arm, to engage and run the nuts down the boltsuntil the nuts are in contact with the rear of the flange face (i e. allnuts are lightly tightened).

The BITT then operates the tensioner jacks 46 (FIG. 6a) to tension thebolts and run down the slackened nuts by operating the BITT motors untilthe motors stall At this point the flanges will closed together andretain the seal.

The tensioning operation is to be performed three times to each bolt,

Once the flange connection has been completed the BITT disengages thereaction nuts and retracts the tensioner magazine leaving the installedbolts in place.

The BITT is the recovered from the spoolpiece C+ by the ROV and deployedback into it's deployment/recovery frame The NM is similarly removedfrom the rigid conduit C and deployed back into said frame.

As described in the previous embodiment, an air hot stab is taken fromthe seal test system (located on the ROV) and is inserted into areceptacle on the mated flange assembly. The said air hot stab ispressurised and the pressure monitored. This provides an external sealtest verify the integrity of the seal between the two conduits,

Once a successful seal test has been completed, the AFT deflectioncylinders are retracted and the clamping modules are once again free tofloat. The pull-in system anchors are disengaged, and the AFT and RTstructure are unlocked from each other, The pipe clamps can now bereleased on the AFT and the AFT can be recovered from the rigidspool-piece C+ and placed back into it's deployment/recovery frame.

Similarly the pipe clamps can now be released on the RT and the RT canbe recovered from the rigid conduit C and placed back into it'sdeployment/recovery frame.

The sequence of events from start to finish is repeated to perform theconnection at the 2nd end of the spoolpiece, i.e connecting rigidspoolpiece C+ to rigid conduit C′. To perform the 2nd end connection theROV will require to re-position the LHF's. The surface support vesselwill recover the FCT and re-load it with a full quota of nuts and bolts,then deploy it once more to the new location on the seabed

Once a successful seal test has been completed at the 2nd end, then thiscompletes the connection of the conduits to form a continuous flowline.

All items are then recovered to the surface, and the ROV performs afinal site survey.

Each step of the above described methods, including all possiblecombinations of them, can be performed without any need for immersedpersonnel.

The use of other types of connection system (clamp, collett or flange)is possible by using the relevant connection tool (torque tool for theclamp screw drives, hydraulic hot stab for the collet, and bolttensioners or torque tools for the flange) forms of which are availableon the market. The procedure to perform a seal test and to replace aseal will also be similar to that outlined above, but using differenttypes of tools which are also readily available on the market.

I claim:
 1. A method of mutually connecting underwater conduits from asupport vessel on the surface comprising the steps of providing a firstand a second underwater conduit, launching a remotely operated vehiclefrom the support vessel; launching connection apparatus having a dockingclamp from the support vessel; manipulating the remotely operatedvehicle to dock with the connection apparatus; installing the connectionapparatus to said first conduit; activating said docking clamp using theremotely operated vehicle to capture the end of the second conduit;activating the connection apparatus to draw the second conduit towardthe first; connecting the two conduits together to form a sealedcontinuous flowline; and recovering the remotely operated vehicle andconnection apparatus to the support vessel.
 2. A method according toclaim 1 and further including the step of supporting one of saidconduits on a frame above the sea bed.
 3. A method according to claim 1or 2, wherein the remotely operated vehicle carries out a survey of thework site and sends a report to the support vessel prior to connectionof the conduits.
 4. A method according to claim 2 wherein the frame isclamped to the conduit.
 5. A method according to claim 4 wherein theremotely operated vehicle docks with the frame and operates the clamp tosecure the conduit thereto.
 6. A method according to claim 1, whereinbuoyancy modules are installed on the second conduit.
 7. A methodaccording to claim 6, wherein the buoyancy modules are inflated from asingle air source, located on the sea bed and operated by the remotelyoperated vehicle.
 8. A method according to claim 7, wherein the remotelyoperated vehicle is operated to adjust the position of the buoyancymodules along the length of the second conduit to adjust the verticalalignment of said conduit prior to connection to the first conduit.
 9. Amethod according to claim 1, wherein the remotely operated vehicle isoperated to remove a cap from the free end of the conduit.
 10. A methodaccording to claim 1, wherein the connection of the two conduits ismonitored by a camera mounted on the remotely operated vehicle.
 11. Amethod according to claim 1, wherein a seal test is performed to verifythe integrity of the seal between the two conduits.
 12. An apparatus formutually connecting underwater conduits being controlled from a supportvessel on the surface, the apparatus comprising a remotely controlledvehicle launchable and recoverable from the support vessel; connectionapparatus for launching and being recoverable from the support vessel;means for docking the remotely operated vehicle to the connectionapparatus; means for mounting the connection apparatus on at least oneof said underwater conduits constituting a first conduit; means providedon the remotely controlled vehicle for capturing the end of the other ofsaid underwater conduits constituting a second conduit and drawing thesecond conduit to the first to enable a connection of the conduitstogether to form a continuous flowline; means to effect the connection;and means for providing a sealed joint at said connection.
 13. Anapparatus according to claim 12 and further comprising an interfaceskid, launchable and recoverable from the support vessel to which theremotely operated vehicle docks in order to provide docking terminalsfor the connection apparatus on the remotely controlled vehicle.
 14. Anapparatus according to claim 12 or 13, comprising a support framelaunched from the support vessel, the support frame being placed aroundone of the conduits by the remotely operated vehicle to raise theconduit from the sea bed.
 15. An apparatus according to claim 14 whereinthe connection apparatus is launched in a sledge from the supportvessel.
 16. An apparatus according to claim 15 wherein an interfacecollar is provided on the free end of the conduits to allow theconnectin apparatus to be mounted in position on the conduits.
 17. Anapparatus according to claim 14 wherein the support frame is alightweight metallic frame substantially h-shaped in configuration. 18.An apparatus according to claim 14 wherein the support frame and theconnection apparatus are substantially neutrally buoyant in water. 19.An apparatus according to claim 12 comprising, an interface skid,launchable and recoverable from the support vessel to which the remotelyoperated vehicle docks in order to provide docking terminals for theconnection apparatus on the remotely controlled vehicle, and comprisinga support frame launched from the support vessel, the support framebeing placed around one of the conduits by the remotely operated vehicleto raise the conduit from the sea bed, and wherein the connectinapparatus is launched in a sledge from the support vessel, and whereinan interface collar is provided on the free end of the conduits to allowthe connection apparatus to be mounted in position on the conduits, andwherein the support frame is a lightweight metallic frame substantiallyh-shaped in configuration, and wherein the support frame and theconnection apparatus are substantially neutrally buoyant in water.